1. Field of the Invention
The present invention relates to a cowling assembly for use on a motorcycle, and more particularly to a cowling assembly to be mounted on a front portion of the frame of a motorcycle.
2. Description of the Relevant Art
Some motorcycles have a cowling mounted on a front portion of the motorcycle frame for reducing the aerodynamic drag and protecting the rider from wind pressure while the motorcycle is running. The cowling is also called a fairing and is finding wide use on many designs of on-road type motorcycles available in recent years.
For protecting the upper half of the body of the rider from wind pressure, it is necessary that a windshield o the cowling project upwardly from the motorcycle frame beyond a certain length. However, the upwardly projecting windshield develops an increased aerodynamic drag. The windshield, especially its upper portion, tends to be deformed easily under applied wind pressure while the motorcycle is running at high speed since the windshield is in the form of a thin panel. The windshield may be prevented from being deformed by increasing the thickness of the windshield itself and its support member for greater rigidity. However, the thicker windshield would result in an increased weight. This would be undesirable since one recent trend in the motorcycle industry is toward lighter motorcycles.
Japanese Laid-Open Utility Model Publication No. 47-859 discloses a cowling assembly including an auxiliary plate positioned on a front portion of the cowling for guiding ram air upwardly to protect the rider against wind pressure. With the auxiliary plate used, the vertical dimension of the windshield can be reduced. However, the disclosed cowling arrangement is not designed for high-speed running of the motorcycle. Inasmuch as the auxiliary plate is exposed out of the cowling, it increases air resistance while the motorcycle is running at high speed.
Another known cowling disclosed in Japanese Laid-Open Utility Model Publication No. 59-54383 (1984) has an air inlet defined in a front portion of the cowling for introducing ram air into the cowling. The cowling also includes a guide plate for guiding the introduced ram air to flow along the inner surface of a windshield. While the ram air is guided along the inner surface of the windshield by the guide plate, it is not guided to a position above the windshield. Therefore, the guide plate is not effective to protect the rider from wind, but only serves to prevent the windshield from being frosted.